which cabinet saw and how to wire for it
rick777
| Posted in Power Tools and Machinery on
I am deciding which cabinet saw to buy between this Spring and early Fall. I have heard good things about all of the ones I am considering; Powermatic 66, Powermatic 2000, Delta Unisaw, Jet, General. Should I consider a 5hp motor or 3hp and should it be wired single phase or three phase and why? I plan to build a metal building shop roughly 30×50 or 40×60 so all the electical wiring options are open for consideration. Thanks for any data, opinions, or experience, you may care to share.
Edited 3/22/2006 10:07 pm ET by rick777
Replies
3hp is plenty for all but the most demanding production shops. Three phase electricity is not generally available to residential homes. Again, this is for industrial shops.
Beat it to fit / Paint it to match
I think 3 phase would be very nice to have, but even if it runs right in front of your shop it would be expensive to install. Your monthly minimum, unless you are a commercial operation would also be very high. The converters probably wouldn't be worth it unless you got the tool dirt cheap. I'm not the expert but just giving you caution.
I'm not an electrician, but am a licensed carpenter and general contractor. We had the same discussion when I built a woodworking shop in an industrial area. Falling back on my experience remodeling a building for a commercial bakery the sparky had to set 3 panels: 1 for 208v 3ph, 1 for 208v 1ph, and 1 for 110v 1ph. Conduits had to be pulled from each panel accordingly and to seperate boxes, no sharing allowed. In the case of my wood shop 3ph was at the pole right outside of my property, but 1ph was available only 1 pole away. Turns out that it was quite a bit cheaper to pay utility to bring the 1ph up 1 pole and only set 1 panel. I have not regretted that decision to date and have plenty of power for whatever. Also, I believe that if you do choose 3ph then the utility will decide that you are a commercial customer and bill you accordingly at a higher rate.
As a side note, sparky tried to tell me that my 240v 1ph unisaw would run fine on 208v 1ph. That is true but if there is ever a brown-out or drop in the voltage while the saw was in use the motor would be fried. That knowledge made me very adamant about bringing in 240v 1ph. Sparky was a little upset about having to wait a couple of weeks for utility to do their thing but later admitted that I was right for being that way. Across the alley from the shop was a light rail train yard that draws 56kv 3ph from the same line that would have fed my shop, increasing the possibility of a brown-out.
As far as the saw goes, those are all good saws. I would put the Powermatic and Delta at the top of the list. Really if I was buying new I would get a Saw Stop.
Three horses is more than adequit unless you are using power feeders and going for real high feed rates. My 3 horse Unisaw is used comercialy and has never lacked power.
Three phase has some pretty big advantages, but they don't really apply to a table saw in a small shop. Three phase motors are instantly reversable, have more low speed torque, can be speed controlled, and don't need a starting circuit. However adding 3 phase to a shop is very costly. EVERY THING three phase is 3 times more expensive. The breaker panel will cost over $500, a 200 amp disconnect is $800 and breakers are $50. In my neck of the woods there was no monthly difference in the KW/hr rate, no minimums or services charges, but there was a $1,000 difference in the installation cost. And this was a new instalation; there was a pole with no lines, or trasformer. The 3 phase power lines were only 30 or 40 feet from the weather head.
Oh yea, if or when you decide to sell the machine it will be a lot harder and you will get a lot less for it.
Mike
I too share your concern for the correct electrical supply . The first electrician read the plate on my delta cabinet saw(3hp) and wired the recepticle with #12 wire, 220, and two pole circutbreaker. The second electrician suggested #10 wire be pulled (conduit) with a 30amp breaker/recepticle. The electrical inspector suggested that I wire direct for 220 with inline control and again reccommended the #10 wire. Would a knowledgeable reader please offer comments.
Edited 3/27/2006 3:30 pm ET by plainjames
Look at the manual and see what it calls for. Generally the wire depends on the aperage draw. Other factors also enter into it like distance. You don't indicate how long the run is, but generall (I say generally) a #12 will support 20amps. Going with a bigger conducter (10 .vs. 12) will not hurt, but is not required. You indicated that the inspector wanted a #10 wire. Was that a suggestion or requirement in your area. A #12 will handle 20 amps. If you run a 10 and latter want to use a 30a device, you would not have to upgrade the wiring, breaker and recepticle. The important part is match the recepticle and wiring, plug, and breaker. If the inspector will not approve if you don't go with the #10, then the whole question seems moot. Good luck.
Thank you for the reply. The inspector did not demand the #10 wire for the saw and I did get the final inspection. The saw recepticle was approx 35' from panel. It seems there is a secondary source for motor use evaluations. I dont know the parameters they consider but the motor label information was only part of the determination. As a result of the expressed concerns I am now wondering if #10 wire @70' will effectively service the 220amp 5hp 2stage compressor with a 30amp breaker. I'm told it will work just fine...
If it's 220 amps, that's one HELL of a compressor. :)My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
I hope I didnt misstate that...the double pole breaker powers at 220volts vrs the normal 110volts...my mistake.
You need to look at amps not volts. I think when you said 220amps you meant 220 volts. If you don't see the amp rating you can figure it. It is volts x watts = amps. The cricial part is not to overload the total rating of the circuit. This includes the wire, recepticle, plug, and breaker. You can use a larger conductor (smaller wire gauge number) to service a lower ratted device, but not the other way around. For example if you total load (amps) is only 20 max, then 12 gauge wire with a 20A nema rated plug will do. If you have over 20A then go up to the 10 gauge wire. I assume this is a dedicated circuit and not being shared. The issue comes in if you wire with a #12 wire and latter want to use a 25A load, you would need to change all the wiring. For me, I made a decision that it is very unlikely that I would upgrade my 3hp 220v TS so the 20A solution worked for me. If I turn out to be wrong, then I would have to upgrade the wiring along with the plug/recepticle and breaker. The most important part is to keep them all on the same rating level and refer to your users manual. In the end, it really comesdown to what is require and what you might want to do in the future. The cost differetial for a number #10 wire for 35 feet seems small, but that's your call. It's just a trip to the hip, as they say.
Watts/Volts =Amps. P=IE
"I cut this piece four times and it's still too short."
"It seems there is a secondary source for motor use evaluations. I dont know the parameters they consider but the motor label information was only part of the determination."
Actually, the secondary source you're thinking of is the primary source, but it's complicated and generally ignored by everyone except electricians and engineers working in commercial and industrial environments. It's NEC Article 430 (Motors, Motor Circuits, and Controllers). Most residential electrical inpsectors don't seem to know much about it, either, and will gig you for following it where it deviates from the general purpose wiring methods.
The basic method is as follows, though there is more to it than this (isn't there always?):
From the motor nameplate HP rating, find FLA (running full-load amperage) from Table 430-148 (for single-phase motors). For a 3 hp motor, it's 17A. You do NOT use the motor's actual FLA.
Size the conductors to 125% of the Table value, or 22A. 12 gauge THHN is rated 25A at either 60ºC or 75ºC, so that is the minimum size allowed. Note that the 20A limit on 12 gauge does not apply to motor circuits - you can use the actual Table 310-16 values.
The circuit breaker can be sized up to 250% of the 17A, or 42.5A, which you can also round up to 45A (next larger standard size - standard per the NEC's definition). That's right, 45A breaker on a 12 gauge circuit. That's because the motor control (required per Article 430) is the circuit overload and overcurrent protection, NOT the CB. The CB is there only for short-circuit and ground-fault protection - it's NOT there to protect the motor against overload per se (that's the job of the control), but it does come into play if the motor shorts internally, and/or the control gets welded closed, ...
The heaters or adjustment in the motor control is set to 15 to 25% over the ACTUAL full-load current shown on the motor nameplate, depending on several factors (like hp, temp rise and service factor).
Any restrictions, like protection type and max value (slow-blow fuses instead of CB, and their max allowed value) on the UL label also must be observed.
As I said, there is more to it, but in general, the nameplate hp rating is what's required to be used to size conductors and controls, not the current rating. Electrical contractors don't even need to know anything but voltage/phase/hp/duty to completely wire an electrical machine, with the final heater sizing being calculated from the nameplate current value.
It's gets a bit slippery when talking about things like a 12.4A 3 hp Unisaw, with a factory cord and plug, which could be considered a UL listed appliance, like your vacuum cleaner or hair dryer (at least in my mind). The manual recommends a 20A 240V circuit, and it will run just fine on a 15A (though not quite legal). Be seeing you...
Thank you !!!
I agree things can get a bit slippery or convoluted when it comes to motor sizing but here is my take on the National Electrical Code
In NEC 2002 article 430.6 (A) (1) there is an exception to using the Table Values to determine motor circuit sizing.
Exception No. 3: For a listed motor-operated appliance that is marked with both motor horsepower and full-load current, the motor full-load current marked on the nameplate of the appliance shall be used instead of the horsepower rating on the appliance nameplate to determine the ampacity or rating of the disconnecting means, the branch circuit conductors, the controller, the branch-circuit shortcircuit and ground-fault protection, and any separate overload protection.
This allows us to take advantage of today's more efficient motors which typically have lower full-load amps than the table values, and size the motor circuit accordingly. For example the 230V Unisaw 12.4FLA motor needs (12.4x125%) =15.5A wire (#14AWG) with a 20A breaker while the table value for 3hp at 17FLA needs (17x125%)=21.25A (#12AWG) and a 25A or 30A breaker. The code does generally limit #14AWG to a 15A breaker and #12AWG to a 20A breaker but not for motor circuits per 240.4(D) & 240.4(G).
The remaining issue is then how far can we run #14AWG or #12AWG wire (I've assumed copper). Using the NEC recommended (but not required as it is a fine print note and therefore not part of the code) 3% voltage drop #14AWG is good for 90-feet and #12AWG is good for 145-feet.
While the above is code as I read it, when it comes to my own garage-workshop I'm about to put in a 60A 240V 1-phase load center and circuits for a 230V table saw plus 120V loads. If I could just make up my miind on what the best table saw is for me to buy (and boy am I having hard time doing this!) AND if it were the Unisaw then I would run #12AWG copper even if the run is only 20-feet. Why? because it will cost only a few pennies more and it would slightly (preceptably or not) improve voltage during starting and heavy loading
-about a new table saw... I thought the DeWalt DW746 was a good buy until I heard of fence and other problems... now I'm wondering about the Unisaw and have yet to read reviews on the new Jet Supersaw hybrid ... I'm also thinking the Beisemeyer fence is a safe bet. ...any suggestions on making this (once-in-a-lifetime) descision would be much appreciated
Cheers
I think you've hit on what causes dissent among electricians (and inspectors) when it comes to home shop wiring. Some folks think you can consider shop equipment to be "motor-driven appliances" and some don't.
The main rationale for sizing your circuit to the HP is the idea that in some future situation, a person might replace one motor with another with the same nominal HP but different current requirements; the other method of sizing the circuit means your wiring will be robust enough for any normal motor of the same HP. Personally, I think it makes sense to use the FLA (with the 25% kick for startup load).
I have a 5HP Unisaw, 21A FLA, so I sized to 30A and ran 10/2 (+ground) to five outlets (and five breakers). The 10/2 cost me maybe $20 total more than if I'd run 12/2, and I can run any equipment I'd seriously consider for my garage shop, in any of five different places. Used NEMA 6-30's (not 6-30L), and I put those on all my 220v tools (now includes BS, TS, jointer, heater). Very flexible, and not at all expensive.My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
I would stay away from the Delta. My industrial machine supplier said Dewalt is running that line into the ground. He would not let me buy a Delta sander because he wasn't sure about reliability in the next few years. The PM 66 is still USA made and and I think the 2000 is made in China. I just bought a Laguna TS and gave my son my 20 year old PM66 and I love this saw. It is bigger, more power, heavier more accurate out of the box and it has a Baldor motor and huge trunnions. The fence is better than my old Biesmeyer (clone) and you can replace the sides. It has a riving knife splitter and it is great. I think they are about the same price. Read FWN review on the Laguna. Don't even think about 3-phase unless all your other machines are 3-phase. Way too expensive.
As my earlier post indicated, I have just completed my electrical inspection of my retirement shop. I chose to utilize the infloor (concrete) hydronic heat (boiler has not been installed yet) and every 4' around the (inside) perimeter of the building I have a combination recepticle housing a 110 duplex and a single 220/20amp. these are located approx 48" from floor. I have two 30 amp 220 , A 40amp 220 and a single 50amp 220. these latter recpt. were for welders. I thought 10' ceiling height would be adequate but on the garage side I can already see that the burning and welding (no built in vent) have affected my white ceiling. Lights are the t8 highoutput and run in two rows for entire length of building. I feed the building with 400amp service and that distributes power thru two 200amp panels and a 100amp second floor sub panel. I would almost have enough room were it not for the old pickup and the car with the dissassembled engine, did i mention i have sons...good luck with your shop.
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